Tractors and other types of mobile heavy equipment (e.g. earth moving, construction, forestry and agricultural machines) are conventionally controlled by an electronic control module (ECM). This device typically comprises a microprocessor that responds to sensed input signals and generates corresponding output signals that control operation of the machinery and its components (e.g. throttle, steering, boom, bucket, mulcher, shredder, or other working head, etc.) in accordance with the sensed input signal. The ECM has also been used in some machines, such as those manufactured by Caterpillar Corporation, as a diagnostic tool to monitor various component systems (e.g. engine, cooling, brakes) of the heavy equipment.
Most types of mobile heavy equipment have traditionally been manned by a human operator who sits on the equipment and sends selected control signals to the ECM via manual controls such as a joystick, lever, etc. In other applications, for example on steep, precipitous or unstable terrain or for the removal of explosives from a battle zone or mined area, it may be extremely dangerous and unacceptable for an operator to personally ride on the equipment. This is particularly so when the machine involved is small and/or compact and does not provide the operator with sufficient protection from an equipment rollover, explosion or other potentially catastrophic event.
Remote control systems have been developed for operating heavy equipment in potentially dangerous applications of the type described above. However, such systems tend to be unduly expensive, complicated and inefficient. This is particularly so when the equipment is already provided with an existing ECM that enables an operator to manually control the machine. In some cases, a separate and/or retrofit receiver/control unit must be programmed independently of the ECM to send output signals to its own dedicated control components (e.g. valves, switches, solenoids). Such remote control systems are expensive and complicated to program, install and maintain. Alternatively, control of the machine can be transferred, as needed, between manual and remote control units through the use of gang relays and other switching systems which are again fairly complex and costly.
The foregoing difficulties can be especially problematic in machines employing an ECM that utilizes pulse width modulated (PWM) control signals. The previously described electronic control module conventionally employed by the machines produced by Caterpillar Corp. is a representative example of a controller that features pulse width modulation. Such ECMs are incompatible with the 1939 CAN communications signal protocol utilized by many standard remote control systems as well as in most conventional heavy equipment control systems. The PWM compatible ECM cannot process CAN Input signals and this cannot be controlled remotely. In the case of the Caterpillar ECM, the extremely useful diagnostic function performed by that controller would be disabled and unavailable during remote control operation. To date, no known control system has been provided for modifying and adapting a pulse width modulation compatible ECM of the type described above so that it is operably responsive to both manually and remotely generated PMW input signals, as well as switched digital inputs. The present invention provides a control system that accomplishes this purpose and overcomes the shortcomings of the prior art.